76 CJ5 258 idles kinda rough. - JeepForum.com
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Unread 02-16-2012, 06:52 PM   #1
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1998 TJ Wrangler 
Join Date: Feb 2012
Location: Louisburg, NC
Posts: 309
76 CJ5 258 idles kinda rough.

It starts just fine (except for a ground problem once in a while) and runs great while at rpm and does not leak a thing. However, it just runs really rough at idle. The previous owner changed the cap, rotor, wires and spark plugs. Has a fairly new carb apparently as well.

It just idles rough and kinda "pops" (however its more of a sucking sound) at idle.

With my very vague description does anyone have any ideas?

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Unread 02-16-2012, 07:03 PM   #2
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1981 CJ5 
Join Date: Sep 2009
Location: Maine
Posts: 1,151
At least for my '77 232, rough idles have usually been caused by vac leaks. Also, the Carter-YF gets easily clogged. When I first got my latest CJ, the idle was cranked super-high to cover up for the fact that it would not idle at all!

The popping might imply the vac leak. Its means the engine is leaning out. Could also be way, way mistimed engine
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Unread 02-16-2012, 11:29 PM   #3
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1981 CJ8 
Join Date: Apr 2010
Location: The Little Apple, KS
Posts: 3,410
My first thought was vacuum leak as well - check all manifold bolts, vacuum lines (PCV, distributor advance vacuum line, etc), carb base screws...

My second thought was a choke plate that isn't set correctly - is it a manual or electronic choke?
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Unread 02-17-2012, 12:24 AM   #4
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1973 CJ5 
Join Date: Aug 2007
Location: South West Indiana
Posts: 11,175
I have to agree, if it pops out the carb, then it's probably lean misfire...

Rebuild carb, use a GOOD fuel filter, and flush the line before you hook up to the carb...

What is your vacuum reading?
Have it running, then spray around intake, carb base plate, vacuum lines, see if your vacuum goes up at any particular spot on the intake run...

Also have a look at the choke, choke problems can cause what you are describing.
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